OF EVOLUTION. 67 



effects which are dependent upon the action of 

 time. The swift-footed animal, which in the pro- 

 cess of rapid locomotion elevates the body so as 

 to weight it principally upon the extremities of the 

 toes, leads the way to the gradual disuse of those 

 toes which, in the required position, are no longer 

 able to give support to the body ; hence, a conse- 

 quent degeneration, and the formation of those 

 apparently " accessory " and more or less func- 

 tionless toes which we see in the hog and many 

 other animals. Similarly, the necessity for a rigid 

 frame combined with lightness would tend to 

 bring about a consolidation of those bones, like 

 the metapodials, whose independent action may 

 now no longer be required. The character of the 

 food supply, necessitating definite methods in the 

 way of eating or mastication, must have a direct 

 effect upon the masticating apparatus, and con- 

 duce toward the formation of the special dental 

 structures which are distinctive of the different 

 animal groups. 



Perhaps no more beautiful illustration of the 



